A method for preparing polylactic acid fiber

Abstract

This invention relates to a method for preparing polylactic acid (PLA) fibers, belonging to the field of fiber manufacturing technology, and solves the problem of poor fiber tow stretching effect. The method for preparing PLA fibers of this invention includes the following steps: Step S1: Mixing raw materials according to a specified ratio and molding by melt extrusion; Step S2: Temperature control of the water bath stretching equipment to achieve a stepped temperature in the water; Step S3: Introducing the PLA fiber tow formed in Step S1 into the water bath stretching equipment and stretching it through the stretching assembly; Step S4: Curling and drying the stretched fiber tow. This invention achieves water bath stretching of fiber tows in water with stepped temperatures, ensuring stretching effect while saving energy.

Description

Technical Field

[0001] This invention relates to the field of fiber manufacturing technology, and in particular to a method for preparing polylactic acid fiber. Background Technology

[0002] Currently, polylactic acid fibers are produced using melt spinning, which requires water bath stretching after filament formation.

[0003] Existing water bath drawing tanks, by incorporating auxiliary tanks and placing the water replenishment tank externally, achieve the goal of reducing the volume of the main tank, making the main tank depth suitable, and not occupying space. However, since the main tank has a certain length, and the hot water in the water replenishment tank is first injected into one end of the main tank, the temperature distribution at both ends of the main tank is uneven, which is not conducive to the water bath drawing effect when multiple fibers are drawn simultaneously.

[0004] Alternatively, the fibers can be heated progressively by setting up multiple water baths with different water temperatures. However, each water bath needs to be equipped with a water pump and a heating unit. In addition, to prevent broken threads from tangling, a broken thread detection unit is required. The broken thread detection unit is completed by multiple optical detection units, which increases the equipment cost and is not conducive to widespread use.

[0005] Therefore, there is a need to provide a method for preparing polylactic acid fibers to improve the stretching effect and minimize costs. Summary of the Invention

[0006] Based on the above analysis, the present invention aims to provide a method for preparing polylactic acid fibers to solve the problems of poor water bath stretching effect and energy waste in existing water bath stretching devices.

[0007] The objective of this invention is mainly achieved through the following technical solutions:

[0008] A method for preparing polylactic acid fiber includes the following steps:

[0009] Step S1: Mix the raw materials according to the specified ratio and then melt-extrude them into shape;

[0010] Step S2: Temperature control is applied to the water bath stretching equipment to create a stepped temperature in the water.

[0011] Step S3: The polylactic acid fiber spun in step S1 is fed into a water bath drawing device and stretched by the drawing assembly;

[0012] Step S4: The filament bundles after water bath stretching are curled and dried for shaping.

[0013] Furthermore, the water bath drawing device includes: a water bath, a water guide plate, a filter box, a drawing assembly, a circulating heating assembly, and a cooling assembly; the water guide plate is inclinedly arranged inside the water bath; the circulating heating assembly is used to drive the water to circulate and heat the water; when the water flows through the water guide plate, it is cooled by the cooling assembly; the drawing assembly is used to press the filament bundle into the water on the water guide plate for water bathing; the filter box is used to filter impurities in the water.

[0014] Furthermore, in step S2, the cooling component includes a blower cooling component and a heat exchange component; the blower cooling component is used to blow air to the filter box to dissipate heat, thereby dissipating heat from the water flowing through the filter box; the heat exchange component includes a heat exchange box for storing the heat exchange medium; the heat exchange box cools the water through heat exchange.

[0015] Furthermore, in step S2, the method for temperature control of the water bath stretching equipment is as follows:

[0016] Step S21: Set the maximum heating temperature of the heating chamber according to the ambient temperature and adjust the maximum temperature of the water.

[0017] Step S22: Set the operating power of the water pump, adjust the flow rate of the water, drive the blades in the transmission box to rotate through the water flow in the water pipe, thereby driving the axial fan blades of the air blowing and heat dissipation component to rotate, and blow air to dissipate heat from the filter box.

[0018] Step S23: Test the water temperature in each area of ​​the water guide plate. If the expected temperature is reached, proceed to step S3; if the expected temperature is not reached, return to steps S21 and S22 for adjustment.

[0019] Furthermore, in step S2, if the ambient temperature is too high and the cooling effect cannot be achieved by the air-blowing heat dissipation component alone, a heat exchange box is installed in the water bath stretching equipment, and the water is cooled by heat exchange through the heat exchange medium in the heat exchange box.

[0020] Further, in step S3, the drawing assembly includes: a guide roller, a traction roller, a first pressure roller, a second pressure roller, and a third pressure roller; the guide roller and the traction roller are respectively disposed at both ends of the water bath; the guide roller and the traction roller rotate at different speeds, which are used to guide the polylactic acid fiber bundles and achieve drawing.

[0021] Furthermore, the first pressing roller, the second pressing roller, and the third pressing roller are all disposed above the water guide plate, for pressing the polylactic acid fiber bundles into the water above the water guide plate; two fixed plates are rotatably mounted on the side wall of the water bath; the second pressing roller and the third pressing roller are both mounted on the two fixed plates through bearings and can move with the fixed plates.

[0022] Further, in step S3, the method for connecting the polylactic acid fiber spinning to the water bath drawing equipment is as follows:

[0023] Step S31: Wind the filament obtained in step S1 onto the guide roller;

[0024] Step S32: Pass one end of the spinning yarn on the guide roller through the underside of the first pressure roller, the third pressure roller and the second pressure roller of the drawing assembly, and then wind it around the traction roller;

[0025] Step S33: Rotate the fixed plate, which drives the second and third pressing rollers to move downwards until the fixed plate is parallel to the water guide plate; then the second and third pressing rollers press the spun yarn into the water above the water guide plate.

[0026] Furthermore, in step S3, two filter boxes are set on the water guide plate; a fixed cover is installed on the outside of the filter boxes; the axial flow fan blade is set in the mounting box, and the mounting box is connected to the fixed cover through two connecting pipes. When the axial flow fan blade rotates, it blows air into the two filter boxes inside the two fixed covers through the two connecting pipes to cool them down; thus, the temperature of the water decreases step by step after flowing through the two filter boxes.

[0027] Furthermore, in step S3, both filter boxes are equipped with baffles and filter screens; the two baffles divide the water guide plate into three sections, thereby dividing the water above the water guide plate into a high-temperature zone, a medium-temperature zone, and a low-temperature zone from top to bottom; the spinning yarn passes through the high-temperature zone, the medium-temperature zone, and the low-temperature zone in sequence under the drive of the guide roller and the traction roller, and undergoes water bath stretching.

[0028] In one specific embodiment of the present invention, the water bath drawing device includes: a water bath, a water guide plate, a filter box, a drawing assembly, a circulating heating assembly, and a blower heat dissipation assembly; the water guide plate is inclinedly arranged inside the water bath, and the internal space of the water bath is divided into an upper part and a lower part by the water guide plate, the upper part is used for fiber bundle water bath, and the lower part is used for water medium circulation;

[0029] The circulating heating assembly includes: a heating tank, a water guide pipe, and a water pump; the heating tank is used to heat water; the water discharged from the heating tank flows from high to low along the upper surface of the water guide plate; the lower end of the water guide plate is provided with a drain hole, which connects the upper and lower parts of the water bath.

[0030] The drawing assembly is used to draw polylactic acid fibers, and at the same time, the polylactic acid fibers are immersed in the water above the water guide plate during drawing for a fiber bundle water bath; the water guide pipe is set at the bottom of the water bath for recycling the water after the fiber bundle water bath; the water pump can pump the water in the water guide pipe into the heating box for water medium circulation.

[0031] Two filter boxes are provided on the water guide plate, which divides the water guide plate into three sections. The filter boxes are used to filter impurities in the water. At the same time, a cooling component is provided below the filter box to cool the water flowing through the filter box.

[0032] The technical solution of this invention can achieve at least one of the following effects:

[0033] 1. The method for preparing polylactic acid fiber of the present invention, by setting an inclined water guide plate, allows water to flow from top to bottom under the action of gravity. After the water flows into the water bath below the water guide plate, the water is driven by a water pump to circulate between the heating box and the water bath, thereby realizing the recycling of water and saving energy.

[0034] 2. The method for preparing polylactic acid fiber of the present invention involves setting a filter box on a water guide plate, and cooling the filter box by a blower and a heat exchanger, so that the temperature of the water flowing through the filter box decreases, thereby achieving a stepped temperature distribution of the water flow on the water guide plate, with the temperature of the water flow above the water guide plate decreasing gradually from high to low. When the polylactic acid fiber bundle is water bath drawn, the higher the water temperature during the water bath, the easier it is to draw and deform; the lower the temperature during the water bath, the higher the degree of curing of the bundle, which is beneficial to improving the structural strength of the bundle after drawing and preventing the bundle from breaking.

[0035] 3. The method for preparing polylactic acid fiber of the present invention uses the flow of water to drive the blades in the transmission box to rotate, which in turn drives the axial flow fan blades to rotate through the vertical rod. Low-temperature air is blown into the fixed cover through the connecting pipe, and the air is blown to dissipate heat from the filter box, thereby reducing the temperature of the water flowing through the filter box. The cooling effect of the water flow enables the supply of water at different temperatures. Compared with the existing multi-group water heating devices, this method reduces the energy consumption and cost of the product.

[0036] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained from what is particularly pointed out in the description and drawings. Attached Figure Description

[0037] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0038] Figure 1 This is a flowchart of the method for preparing polylactic acid fibers according to the present invention;

[0039] Figure 2 This is a schematic diagram of the water bath stretching equipment used in the preparation method of polylactic acid fiber of the present invention;

[0040] Figure 3 This is a top view schematic diagram of the water bath stretching device of the present invention;

[0041] Figure 4 This is an exploded view of the filter box and baffle plate of the water bath stretching device of the present invention;

[0042] Figure 5 for Figure 1 Enlarged view of point A in the middle;

[0043] Figure 6 This is a cross-sectional schematic diagram of the first pressing roller and rotating rod of the water bath drawing device of the present invention;

[0044] Figure 7 This is a top cross-sectional view of the transmission box of the water bath stretching device of the present invention.

[0045] Figure 8 This is a top cross-sectional view of the heating box of the water bath stretching device of the present invention;

[0046] Figure 9 for Figure 1 Enlarged view of point B in the middle;

[0047] Figure 10 This is a side view of the fixing frame and metal spring sheet of the water bath stretching device of the present invention;

[0048] Figure 11 A side view of the water bath tank of the water bath stretching device of the present invention with ventilation holes;

[0049] Figure 12 A side view of the water bath tank of the water bath stretching device of the present invention with an air inlet hole;

[0050] Figure 13 This is a schematic diagram of the heat exchange box of the water bath stretching device of the present invention.

[0051] Figure label:

[0052] 1-Water bath; 2-Water guide plate; 3-Through groove; 4-Filter box; 5-Drain hole; 6-Water baffle; 7-Filter screen; 8-Vertical plate; 9-Rotating roller; 10-Clamping block; 11-Guide roller; 12-Traction roller; 13-First pressure roller; 14-Second pressure roller; 15-Third pressure roller; 16-Fixing plate; 17-Rotating rod; 18-Fixing frame; 19-Metal spring; 20-Side plate; 21-Guide pulley; 22-Limiting rod; 23-Partition plate ; 24-Water collection chamber; 25-First conduit; 26-Second conduit; 27-Third conduit; 28-Heating box; 29-Heating wire; 30-Water outlet; 31-Transmission box; 32-Vertical rod; 33-Blade; 34-Mounting box; 35-Fixing cover; 36-Heat-conducting fins; 37-Connecting pipe; 38-Ventilation hole; 39-Air inlet; 40-Heat exchange box; 41-Medium tank; 42-Handle; 43-Inner side of heat exchange box; 44-Outer side of heat exchange box. Detailed Implementation

[0053] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which constitute a part of the present invention and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0054] Example 1

[0055] A specific embodiment of the present invention discloses a method for preparing polylactic acid fibers, such as... Figure 1 As shown, a method for preparing polylactic acid fiber includes the following steps:

[0056] Step S1: Mix the raw materials according to the specified ratio and then melt-extrude them into shape;

[0057] Step S2: Temperature control is applied to the water bath stretching equipment to create a stepped temperature in the water.

[0058] Step S3: The polylactic acid fiber spun in step S1 is fed into a water bath drawing device and stretched by the drawing assembly;

[0059] Step S4: The filament bundles after water bath stretching are curled and dried for shaping.

[0060] In step S1, the melt extrusion formed filament bundle is a pre-formed polylactic acid fiber. After the pre-formed filament bundle is drawn and elongated, the formed filament bundle can be obtained.

[0061] In one specific embodiment of the present invention, the water bath stretching device includes: a water bath 1, a water guide plate 2, a filter box 4, a stretching assembly, a circulating heating assembly, and a cooling assembly; the water guide plate 2 is inclinedly arranged inside the water bath 1; the circulating heating assembly is used to drive the water to circulate and heat the water; when the water flows through the water guide plate 2, it is cooled by the cooling assembly; the stretching assembly is used to press the filament bundle into the water on the water guide plate 2 for water bathing; the filter box 4 is used to filter impurities in the water.

[0062] In step S2, the cooling component includes a blower cooling component and a heat exchange component; the blower cooling component is used to blow air to the filter box 4 to dissipate heat, thereby dissipating heat from the water flowing through the filter box 4; the heat exchange component includes a heat exchange box 40 that stores the heat exchange medium; the heat exchange box 40 cools the water through heat exchange.

[0063] In step S2, if the ambient temperature is too high and the cooling effect cannot be achieved by the air-blowing heat dissipation component alone, a heat exchange box 40 is installed in the water bath stretching equipment, and the water is cooled by heat exchange through the heat exchange medium in the heat exchange box 40.

[0064] In one specific embodiment of the present invention, such as Figure 2 As shown, in step S2, the internal space of the water bath 1 is divided into an upper part and a lower part by the water guide plate 2. The upper part is used for the fiber bundle water bath, and the lower part is used for water medium circulation.

[0065] In step S2, when the water bath drawing equipment performs water bath spinning, it uses a circulating heating component to provide recyclable water and can control the water temperature.

[0066] The circulating heating assembly includes: a heating tank 28, a water guide pipe, and a water pump; the heating tank 28 is used to heat water; the water discharged from the heating tank 28 flows from high to low along the upper surface of the water guide plate 2; the lower end of the water guide plate 2 is provided with a drain hole 5, which connects the upper and lower halves of the water bath 1; the drawing assembly is used to draw polylactic acid fibers, while simultaneously immersing the polylactic acid fibers in the water above the water guide plate 2 for a fiber bundle water bath during drawing; the water guide pipe is provided with... The water is placed at the bottom of the water bath 1 to recover the water after the fiber bundle water bath; the water pump can pump the water in the water guide pipe into the heating box 28 for water medium circulation; two filter boxes 4 are provided on the water guide plate 2, and the filter boxes 4 divide the water guide plate 2 into three sections; the filter boxes 4 are used to filter impurities in the water, and at the same time, a blower heat dissipation component and / or heat exchange component are provided below the filter boxes 4, and the blower heat dissipation component and / or heat exchange component are used to cool the water flowing through the filter boxes 4.

[0067] In step S2, the bottom end of the water guide plate 2 has multiple drainage holes 5, and the interior of the water bath 1 is divided into upper and lower parts by the water guide plate 2. The upper part is used for the fiber bundle water bath, and the lower part is used for water medium circulation; for example Figure 3 As shown. The hot water flowing out of the heating box 28 flows sequentially through the upper surface of the multi-section water guide plate 2 and the filter box 4, and then flows into the water collection chamber 24 below the water guide plate 2 through multiple drain holes 5.

[0068] Preferably, the surface of the water guide plate 2 is provided with corrugations extending along the direction of the filament movement; the trough area of ​​the corrugations has a certain water storage function, which can reduce the flow speed of the water, and at the same time, the trough has the effect of promoting the water to extend perpendicular to the direction of the filament movement, so that the water is evenly distributed on the surface of the water guide plate 2, thereby enabling multiple rows of filaments to be immersed in the water and the water temperature to tend to be uniform.

[0069] Specifically, the side wall of the water guide plate 2 is welded to the inner wall of the water bath 1. When the water flows in the upper part, the wire bundle water bath can be carried out. After the water flows to the lower part through the drain hole 5, it can be heated and flow back to the upper part, thereby realizing the water circulation and continuous water bath operation.

[0070] like Figure 2 As shown, a partition 23 is welded to the inner wall of the water bath 1, and the partition 23 is vertically arranged between the water guide plate 2 and the bottom plate of the water bath 1. Specifically, the drain hole 5 is located between the partition 23 and the wall of the water bath 1. The upper end of the partition 23 is welded and fixed to the water guide plate 2, and the lower end of the partition 23 is welded and fixed to the bottom plate of the water bath 1. The two sides of the partition 23 are in sealed contact or sealed connection with the two side walls of the water bath 1, thereby forming a water collection cavity 24 between the partition 23, the water guide plate 2, and the inner wall of the water bath 1. The water collection cavity 24 is connected to the drain hole 5, so the water collection cavity 24 can collect the water flowing down from the drain hole 5.

[0071] The heating box 28 is located at the top of the water bath 1. The water outlet 30 on the heating box 28 is located above the top of the water guide plate 2, so that after the water is heated, it will flow into the top of the water guide plate 2 through the water outlet 30. In this way, the water can flow down the water guide plate 2 again, so that the water can flow continuously on the surface of the water guide plate 2 to ensure the circulation of the water bath operation.

[0072] In step S2, the circulating water supply method of the circulating heating component is as follows:

[0073] Step S201: After the heating box 28 heats the water, the water flows out through the water outlet 30 at the bottom of the heating box 28; after flowing out, the water falls to the highest end of the water guide plate 2 and then flows along the water guide plate 2.

[0074] Step S202: The water flows to the drain hole 5 at the end of the water guide plate 2 and flows into the water collection cavity 24 below the water guide plate 2 through the drain hole 5;

[0075] Step S203: After the water flows through the drain hole 5 on the water guide plate 2 to the water collection chamber 24, it is guided through the water guide pipe. The water in the water guide pipe is pumped back into the heating box 28 for heating by the water pump, so as to realize the circulating water supply.

[0076] like Figure 3 , Figure 4 As shown, the water guide plate 2 is provided with a through groove 3, and the filter box 4 is fixedly installed in the through groove 3 and located below the water guide plate 2; the filter box 4 is provided with a baffle plate 6 and a filter screen 7 inside; the baffle plate 6 is set perpendicular to the water guide plate 2, and its upper end protrudes from the upper surface of the water guide plate 2; the filter screen 7 is installed between the baffle plate 6 and the filter box 4, so that the baffle plate 6 and the filter screen 7 can divide the internal cavity of the filter box 4 into left and right parts; when the water flows through the filter screen 7, it can filter impurities.

[0077] like Figure 3 , Figure 4 As shown, a set of through grooves 3 are provided on the water guide plate 2. A filter box 4 is inserted into the through groove 3 and welded to it. A water blocking component is inserted inside the filter box 4. The water blocking component includes a water blocking plate 6 and a filter screen 7. The filter screen 7 is welded to the water blocking plate 6.

[0078] Specifically, such as Figure 4 , Figure 5 As shown, the filter screen 7 is inserted into the filter box 4 and fits against the inner wall of the filter box 4.

[0079] Specifically, two clamping blocks 10 are welded to the inner walls of both sides of the filter box 4, and the inner sides of the two clamping blocks 10 are in contact with the two end sides of the baffle plate 6.

[0080] Preferably, the baffle plate 6 and the retaining block 10 are connected by magnetic attraction. Specifically, a first magnet is embedded in the retaining block 10 at the position where it fits against the baffle plate 6. The baffle plate 6 is made of metal or has a second magnet with opposite magnetic poles to the first magnet. When the baffle plate 6 is inserted between the two retaining blocks 10, they are attracted by magnetic force. The baffle plate 6 of this invention is inserted into the filter box 4 by magnetic attraction, which allows for quick insertion and removal, facilitating installation, disassembly, and cleaning of the filter screen 7.

[0081] In step S2, the two baffles 6 in the filter box 4 can divide the water guide plate 2 into three sections, each of which can form a water bath area. Due to the setting of the baffles 6, the water must flow through the filter box 4 when it flows down the water guide plate 2. The water is filtered by the filter screen 7 in the filter box 4 and then flows out of the filter box 4 from the other side of the baffles 6 to ensure the cleanliness of the water. At the same time, by cooling the filter box 4, the temperature of the water can be controlled, so that the three water bath areas have a stepped temperature.

[0082] The three-stage water bath in this invention can heat water using only one set of water pumps and heating wires, and the wire breakage detection is achieved through a physical structure, which greatly reduces equipment costs and operational difficulty, and is conducive to widespread use.

[0083] Furthermore, such as Figure 4 , Figure 5 As shown, the outer side of the filter box 4 is provided with a plurality of heat-conducting fins 36 for heat dissipation.

[0084] like Figure 5 As shown, the heat-conducting fins 36 are rectangular plate structures; multiple heat-conducting fins 36 are integrally formed on both outer walls of the filter box 4. The filter box 4, together with the heat-conducting fins 36, can conduct heat and dissipate heat from the water flow, thereby reducing the water temperature and making the temperature of each water bath zone different. This is beneficial to the stretching effect of the filament bundle when it passes through three water bath zones with different temperatures, thus improving the strength of the filament bundle.

[0085] In step S2, the temperature of the water bath stretching equipment is controlled as follows:

[0086] Step S21: Set the maximum heating temperature of the heating box 28 according to the ambient temperature, and adjust the maximum temperature of the water.

[0087] Step S22: Set the operating power of the water pump, adjust the flow rate of the water, drive the blades 33 in the transmission box 31 to rotate through the water flow, thereby driving the axial fan blades of the air blowing and heat dissipation component to rotate, and blow air to cool the filter box 4.

[0088] Step S23: Test the water temperature in each area of ​​the water guide plate 2. If the expected temperature is reached, proceed to step S3; if the expected temperature is not reached, return to steps S21 and S22 to adjust again.

[0089] Specifically, the temperature range of the water bath is T1 - T2, and the median value of T1 and T2 is T3. When the ambient temperature is too high, the water body cools slowly. The maximum heating temperature T of the heating box 28 is set to be higher than the minimum value of the water bath temperature range and lower than the median value, that is, T1 < T < T3, to ensure the temperature gradient in the high-temperature, medium-temperature, and low-temperature zones. When the ambient temperature is too low, the water body cools quickly. The maximum heating temperature T of the heating box 28 is set to the maximum value of the water bath temperature range, that is, T = T2, to achieve a good drafting effect. When the ambient temperature is in a general state, that is, when the ambient temperature is between 0°C and 30°C, the maximum heating temperature T of the heating box 28 is set to be higher than the median value of the water bath temperature range, that is, T3 < T < T2. Exemplarily, the temperature range of the water bath is 50°C - 70°C.

[0090] In a specific embodiment of the present invention, as Figure 4 , Figure 5 shown, the blowing and heat dissipation component includes: a fixed cover 35, a connecting pipe 37, and an installation box 34. Ventilation holes 38 are provided on the side surface of the water bath 1. The fixed cover 35 is fixedly connected to the inner wall surfaces on both sides of the water bath 1 and is connected to the ventilation holes 38. The fixed cover 35 covers the outside of the filter box 4 and is connected to the installation box 34 through the connecting pipe 37. A rotatable axial flow fan blade is installed in the installation box 34. When the axial flow fan blade rotates, it can promote air to flow from the connecting pipe 37 into the fixed cover 35, and then blow and dissipate heat from the filter box 4.

[0091] As Figure 2 and Figure 5 shown, a fixed cover 35 is sleeved around the filter box 4. The cross-section of the fixed cover 35 is a U-shaped structure. The two ends of the fixed cover 35 are welded to the inner wall of the water bath 1, and the top end of the fixed cover 35 is welded to the bottom surface of the water guide plate 2. Ventilation holes 38 are provided on the wall body of the water bath 1. One end of the fixed cover 35 is connected to the ventilation holes 38. A connecting pipe 37 is welded and connected to the side wall of the fixed cover 35. The connecting pipes 37 on the two fixed covers 35 are connected through a three-way connection.

[0092] Since water continuously flows on the surface of the water guide plate 2, in order to ensure the heat conduction effect of the heat conduction fins 36, it is necessary to cool the heat conduction fins 36. Therefore, the airflow generated by the axial flow fan blade can enter the connecting pipe 37 through the three-way connection, and finally the airflow enters the fixed cover 35 and is discharged from the ventilation holes on the wall body of the water bath 1. Through the continuous flow of air, the heat conduction efficiency of the heat conduction fins 36 is accelerated, so that the heat conduction fins 36 can always cool the water flow.

[0093] As Figure 7As shown, a transmission box 31 is installed on the water guide pipe; a vertical rod 32 and blades 33 are installed in the transmission box 31; the lower end of the vertical rod 32 is rotatably connected to the transmission box 31, and the upper end is fixedly connected to the axial flow fan blades; the blades 33 are fixedly installed on the outside of the vertical rod 32, and multiple blades are arranged circumferentially; when the water in the water guide pipe flows through the transmission box 31, it can drive the blades 33 to rotate; when the blades 33 rotate, they can drive the vertical rod 32 and the axial flow fan blades to rotate.

[0094] like Figure 2 As shown, one end of the water guide pipe is connected to the water collection chamber 24, and the other end is connected to the heating box 28; the water pump is installed on the water guide pipe. Specifically, the water guide pipe includes: a first conduit 25, a second conduit 26, and a third conduit 27, wherein one end of the first conduit 25 is connected to the water collection chamber 24, and the other end is connected to the transmission box 31; one end of the second conduit 26 is connected to the transmission box 31, and the other end is connected to the water pump; one end of the third conduit 27 is connected to the water pump, and the other end is connected to the heating box 28.

[0095] Specifically, such as Figure 2 As shown, a water pump is bolted to the inner wall of the water bath 1. The inlet and outlet ends of the water pump are connected to a second conduit 26 and a third conduit 27 via flanges, respectively. The second conduit 26 is connected to the first conduit 25 via a transmission box 31. The first conduit 25 passes through the partition 23 and extends into the water collection chamber 24. One end of the third conduit 27 passes through the water bath 1 and is connected to the bottom of the heating box 28. Thus, the water pump can draw out the water accumulated in the water collection chamber 24 and pump it into the heating box 28. After being heated again by the heating box 28, the water flows out to the water guide plate 2 for water bath stretching operation, realizing the circulation and use of the water.

[0096] Specifically, such as Figure 7 As shown, the first conduit 25 and the second conduit 26 are offset in the radial direction of the transmission box 31, so that when the water flows between the first conduit 25, the transmission box 31 and the second conduit 26, it can drive the blades 33 inside the transmission box 31 to rotate.

[0097] like Figure 2 , Figure 8 As shown, the heating box 28 is located on one side of the water bath 1. A set of heating wires 29 are installed on the inner wall of the heating box 28, and multiple water outlet holes 30 are opened on the side of the heating box 28 facing the water guide plate 2. After the water is heated in the heating box 28 by the heating wires 29, it flows out through the water outlet holes 30 and then flows to the water guide plate 2 to perform water bath stretching of polylactic acid fibers.

[0098] Specifically, such as Figure 2 , Figure 7As shown, the mounting box 34 is fixedly installed above the transmission box 31. The transmission box 31 is a hollow cylinder, and a vertical rod 32 is connected to the center of the top wall of the transmission box 31 via a bearing. The vertical rod 32 penetrates the top wall of the transmission box 31, with its bottom end extending into the transmission box 31 and its top end extending into the mounting box 34. A blade 33 is fixed to the outer cylindrical surface of the end of the vertical rod 32 located inside the transmission box 31 by a locking pin, and an axial flow fan blade is fixed to the end of the vertical rod 32 that extends into the mounting box 34 by a locking pin. When the water flow in the water pipe drives the blade 33 to rotate, the blade 33 drives the axial flow fan blade to rotate synchronously via the vertical rod 32.

[0099] Furthermore, such as Figure 12 As shown, the side of the water bath 1 is also provided with an air inlet 39; used to introduce ambient air into the interior of the water bath 1. Specifically, the air inlet 39 connects to the space in the water bath 1 located below the water guide plate 2 and is located outside the water collection cavity 24.

[0100] Furthermore, the mounting box 34 has multiple openings at its bottom end, which are connected to the air inlet 39 of the water bath 1 to provide air for blowing onto the fixing cover 35. Alternatively, the mounting box 34 is connected to the air inlet 39 via an air inlet pipe.

[0101] Furthermore, the number of connecting pipes 37 is the same as the number of fixing covers 35, and each fixing cover 35 has a connecting pipe 37 connected to its side. Multiple connecting pipes 37 are directly connected to the mounting box 34; or multiple connecting pipes 37 are connected to the mounting box 34 through a multi-port structure.

[0102] For example, such as Figure 2 As shown, there are two connecting pipes 37 and two fixing covers 35. The two connecting pipes 37 are respectively connected to the two ports of the three-way pipe. The top of the mounting box 34 is connected to the remaining port of the three-way pipe through a flexible tube. When the axial fan blades in the mounting box 34 rotate, they can blow air into the three-way pipe, which then splits the air into the two connecting pipes 37, and finally blows the air into the fixing cover 35 through the two connecting pipes 37.

[0103] Furthermore, in step S22, the method by which the cooling assembly cools the filter box 4 is as follows:

[0104] Step S221: When the water in the first conduit 25 enters the transmission box 31, the power of the water flow will drive the vertical rod 32 to rotate, and then the vertical rod 32 can drive the axial fan blade to rotate in the mounting box 34.

[0105] Step S222: Air entering the water bath 1 through the air inlet 39 enters the mounting box 34 through the opening at the bottom of the mounting box 34 or the air inlet pipe, and the rotating axial fan blades can generate airflow, which flows into the fixed cover 35 through the connecting pipe 37.

[0106] Step S223: The airflow flowing into the fixed cover 35 exchanges heat with the filter box 4 and the heat-conducting fins 36 to achieve heat dissipation of the filter box 4 by blowing air. The gas after heat exchange is discharged through the ventilation hole 38 on the side of the water bath 1.

[0107] In step S222, two filter boxes 4 are set on the water guide plate 2, and correspondingly, two fixed covers 35 are respectively installed on the outside of the two filter boxes 4. The axial flow fan blades are set in the mounting box 34, and the mounting box 34 is connected to the two fixed covers 35 through two connecting pipes 37. When the axial flow fan blades rotate, they blow air to the two filter boxes 4 inside the two fixed covers 35 through the two connecting pipes 37 to cool them down. As a result, the water temperature decreases step by step after flowing through the two filter boxes 4.

[0108] In steps S2 and S3, when the ambient temperature is too high and the cooling effect of blowing air alone is insufficient to meet the cooling requirements of the high-temperature water, a heat exchange box 40 is installed in the fixed cover 35 in order to further improve the cooling effect of the high-temperature water flowing out of the heating box 28.

[0109] like Figure 11 As shown, a heat exchange box 40 is slidably installed in the fixed cover 35; the heat exchange box 40 is filled with a cooling medium that can cool the filter box 4.

[0110] like Figure 11 , Figure 13 As shown, the heat exchange box 40 is U-shaped; the outer side 44 of the heat exchange box 40 is fitted with the inner wall of the fixing cover 35, and does not obstruct the air outlet of the connecting pipe 37; the inner side 43 of the heat exchange box 40 is fitted with the outer surface of the filter box 4. During installation, the heat exchange box 40 slides into the fixing cover 35 through the vent 38, and is supported and fixed by the fixing cover 35, achieving a pull-out installation.

[0111] For example, the cooling medium is ice, thermally conductive silicone at low temperature, or other phase change material at low temperature.

[0112] Specifically, the heat exchange box 40 is provided with a medium tank 41 for filling the heat exchange medium; the outer end face of the heat exchange box 40 is provided with a handle 42, which is used to slide the heat exchange box 40 in the fixed cover 35 for installation or removal.

[0113] The present invention cools the filter box 4 by means of the cooling medium in the heat exchange box 40, which can cool the high temperature water in a short time and make the water temperature in different areas above the water guide plate 2 have a large temperature difference, which is conducive to the reliable realization of the three-stage water bath of polylactic acid fiber.

[0114] The drawing assembly of the present invention includes: a rotating roller 9, a guide roller 11, a traction roller 12, a first pressure roller 13, a second pressure roller 14, and a third pressure roller 15; the guide roller 11 and the traction roller 12 are respectively disposed at both ends of the water bath 1, and their rotation speeds are different, used to guide the polylactic acid fiber bundles and achieve drawing, as shown below. Figure 2 As shown.

[0115] The first pressing roller 13 and the second pressing roller 14 are respectively disposed at both ends of the water guide plate 2, and are used to press the polylactic acid fiber bundle into the water above the water guide plate 2; a rotating roller 9 is rotatably installed on the upper end of each water baffle plate 6; two third pressing rollers 15 are respectively disposed on both sides of each rotating roller 9; multiple third pressing rollers 15, the first pressing roller 13 and the second pressing roller 14 are located on the same straight line; the rotating roller 9 is disposed above the straight line formed by the connection of the first pressing roller 13 and the second pressing roller 14.

[0116] In one specific embodiment of the present invention, such as Figure 4 , Figure 5 As shown, two vertical plates 8 are welded to the top of the baffle plate 6. The two vertical plates 8 are set perpendicular to the baffle plate 6 and are located at the left and right ends of the baffle plate 6. A rotating roller 9 is rotatably connected between the two vertical plates 8 through a rotating shaft.

[0117] like Figure 2 , Figure 3 and Figure 6 As shown, the drawing assembly includes a guide roller 11 and a traction roller 12 located at both ends of the water bath 1, and a first pressure roller 13, a second pressure roller 14 and a third pressure roller 15 located between the guide roller 11 and the traction roller 12; the third pressure roller 15 is arranged in pairs, and at least two pairs are provided.

[0118] In one specific embodiment of the present invention, the first pressing roller 13, the second pressing roller 14 and the third pressing roller 15 are all disposed above the water guide plate 2, for pressing the polylactic acid fiber bundle into the water above the water guide plate 2.

[0119] like Figure 3 As shown, both ends of the multiple third pressing rollers 15 and the second pressing roller 14 are rotatably connected to the two fixed plates 16 via bearings; therefore, the second pressing roller 14 and the third pressing roller 13 can rotate relative to the fixed plate 16, and when the fixed plate 16 is displaced, the second pressing roller 14 and the third pressing roller 13 are also displaced synchronously.

[0120] Specifically, such as Figure 3 , Figure 6As shown, one end of each of the two fixed plates 16 is provided with a rotating rod 17 welded to it, and both ends of the rotating rod 17 pass through the two fixed plates 16; both ends of the rotating rod 17 are movably connected to the bearings on the side wall of the water bath 1, and are driven to rotate by a motor; when the rotating rod 17 rotates, the fixed plates 16 also rotate synchronously.

[0121] like Figure 2 , Figure 3 As shown, when the rotating rod 17 rotates, the fixed plate 16 also rotates around the rotating rod 17 as an axis, causing multiple third pressing rollers 15 and second pressing rollers 14 to move relative to the water bath 1; then multiple third pressing rollers 15 and second pressing rollers 14 are pressed down into the water above the water guide plate 2.

[0122] Furthermore, the first pressing roller 13 is a hollow cylindrical tube and is sleeved on the rotating rod 17 through a bearing, so that the first pressing roller 13 can rotate relative to the rotating rod 17.

[0123] In step S3, the method for connecting the polylactic acid fiber spinning to the water bath drawing equipment is as follows:

[0124] Step S31: Wind the spun yarn obtained in step S1 onto the guide roller 11;

[0125] Step S32: Pass the wire bundle on the guide roller 11 through the bottom of the first pressure roller 13, the second pressure roller 14 and the third pressure roller 15 in sequence, and wind and fix it on the traction roller 12;

[0126] Step S33: Rotate the fixed plate 16, which drives the second pressing roller 14 and the third pressing roller 15 to move down until the fixed plate 16 is parallel to the water guide plate 2; then the second pressing roller 14 and the third pressing roller 15 press the spinning into the water above the water guide plate 2.

[0127] Specifically, in step S33, the rotating rod 17 is driven to rotate by the motor, and the rotating rod 17 drives the fixed plate 16 to rotate. The fixed plate 16 screws the second pressing roller 14 and the third pressing roller 15 into the water bath 1. This can press the wire bundle into the water above the water guide plate 2. When the third pressing roller 15 presses down, it works with the rotating roller 9 to lift the middle part of the wire bundle upward, which can keep the wire bundle in a taut state and prevent the wire bundle from scratching the water baffle plate 6.

[0128] In step S3, by changing the ratio of the linear speed of the traction roller 12 and the guide roller 11, after adjusting to a suitable draw ratio, the filament bundle can be pulled to move continuously for water bathing, while stretching the filament bundle.

[0129] Specifically, such as Figure 3As shown, the part of the baffle plate 6 that protrudes from the filter box 4 is sealed and fitted with the fixing plate 16. In this way, the water flow will only flow on the surface of the guide plate 2, and when it flows, it will flow into the filter box 4 under the obstruction of the baffle plate 6. Then, after passing through the filter screen 7, it will flow out from the other side of the filter box 4 to the next section of the guide plate 2.

[0130] In step S3, both filter boxes 4 are equipped with baffle plates 6 and filter screens 7; the two baffle plates 6 divide the water guide plate 2 into three sections, and then, under the action of the cooling component, the water above the water guide plate 2 is divided into a high temperature zone, a medium temperature zone and a low temperature zone from top to bottom; the spinning yarn passes through the high temperature zone, the medium temperature zone and the low temperature zone in sequence under the drive of the guide roller 11 and the traction roller 12, and is subjected to water bath stretching.

[0131] In step S3, when the polylactic acid fiber bundle passes through the high-temperature zone, the bundle will stretch due to the speed difference between the guide roller 11 and the traction roller 12; when the polylactic acid fiber bundle passes through the medium-temperature zone, the bundle structural strength increases and the stretchability decreases, but it still has a stretching effect; when the polylactic acid fiber bundle passes through the low-temperature zone, the bundle structural strength further increases and the stretchability is at its lowest, reducing the risk of breakage of the bundle that has already been stretched after passing through the high-temperature zone and the medium-temperature zone.

[0132] In one specific embodiment of the present invention, such as Figure 9 , Figure 10 As shown, it also includes: a broken fiber detection component; the broken fiber detection component includes: a fixing frame 18, a metal spring 19, a guide pulley 21, and a limiting rod 22; the fixing frame 18 is in the shape of a "door" and is fixedly installed on the water bath 1; multiple metal springs 19 are arranged side by side on the crossbeam of the fixing frame 18; the end of the metal spring 19 is rotatably mounted with the guide pulley 21, one end of the limiting rod 22 is fixedly connected to the crossbeam of the fixing frame 18, and the other end is located on one side of the metal spring 19; the polylactic acid fiber bundle passes around the guide pulley 21, and then when the bundle is stretched, the pressure on the guide pulley 21 can press the metal spring 19 tightly against the end of the limiting rod 22 so that the two abut against each other.

[0133] like Figure 2 , Figure 9 and Figure 10 As shown, a wire breakage detection assembly is installed directly below the traction roller 12. The fixing frame 18 of the wire breakage detection assembly is fixedly installed by welding at the end of the water bath 1 where the heating box 28 is not installed. Furthermore, multiple metal springs 19 are welded at equal intervals on the fixing frame 18.

[0134] Specifically, such as Figure 9 As shown, two side plates 20 are welded to the bottom front of the metal spring 19, and a guide wire pulley 21 is rotatably installed between the two side plates 20 through a bearing and a rotating shaft.

[0135] Specifically, such as Figure 9 As shown, the bottom back of the metal spring 19 abuts against the end of the limiting rod 22, and the other end of the limiting rod 22 is welded and fixed to the fixing frame 18.

[0136] Specifically, such as Figure 10 As shown, multiple metal springs 19 and multiple guide pulleys 21 are arrayed, which enables simultaneous detection of broken fibers in multiple groups of polylactic acid fiber bundles.

[0137] When the traction roller 12 starts to stretch the filament bundle, the filament bundle receives tension, and the tension also acts on the metal spring 19, causing the metal spring 19 to deform to a certain extent until the bottom end of the metal spring 19 abuts against the end of the limiting rod 22. When the filament bundle breaks, the force on the metal spring 19 disappears, and then the metal spring 19 will deform and reset, thus reminding the staff that the filament bundle is broken. At the same time, when the metal spring 19 resets, it will pull the broken filament bundle in the opposite direction to prevent entanglement when it breaks.

[0138] Furthermore, an inspection port is provided on the side wall of the water bath 1 where the water pump is installed, which facilitates the maintenance and repair of the internal components.

[0139] Compared with the prior art, the technical solution provided in this embodiment has at least one of the following beneficial effects:

[0140] 1. The method for preparing polylactic acid fiber of the present invention includes an inclined water guide plate 2 for guiding water flow, so that the water flow can continuously flow downward along the water guide plate 2. The water guide plate 2 can be divided into three sections by two baffle plates 6. When the water flows downward through one baffle plate 6, it will be filtered through the filter box 4, so that impurities in the water flow can be separated and prevented from adhering to the fiber bundle, thus ensuring the quality of the fiber bundle.

[0141] 2. The method for preparing polylactic acid fiber of the present invention uses heat-conducting fins 36 on the filter box 4 to cool the water flow, and a baffle plate 6 is set so that the water flow must pass through the filter box 4 before flowing to the next section. In this way, the temperature of the water flow will drop a little each time it passes through a filter box 4. After the water flow enters the filter box 4, the temperature of the water flow will be conducted to the filter box 4, and the temperature of the filter box 4 will be conducted to the air through the heat-conducting fins 36, thereby achieving the cooling of the water flow. This ensures that the temperature of the three water bath areas on the water guide plate gradually decreases from top to bottom. As a result, the water temperature in the upper section of the water guide plate 2 is the highest, the water temperature in the middle section is in the middle, and the water temperature in the bottom section is the lowest, thus realizing a three-stage water bath, which is beneficial to improving the water bath effect.

[0142] 3. The method for preparing polylactic acid fiber of the present invention includes a broken fiber detection component. During fiber strand stretching, the tension of the fiber strand stretching provides a clamping force on the guide pulley 21, which in turn presses down the metal spring 19. When the fiber strand breaks, the clamping force disappears, and the metal spring 19 is reset to detect the broken fiber. Simultaneously, after reset, the guide pulley 21 synchronously moves the end of the metal spring 19, which can drive the broken fiber to pop out, thereby preventing the broken fiber strand from entangled with other normal fiber strands.

[0143] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for producing a polylactic acid fiber, characterized by, The method comprises the following steps: Step S1: mixing raw materials according to a specified ratio and forming by melt extrusion; Step S2: temperature regulation of the water bath drafting device to make the water body have a step temperature; Step S3: spinning the polylactic acid fiber formed in step S1 into the water bath drafting device and stretching by a drafting assembly; Step S4: crimping and drying the filament bundle after water bath drafting and setting the shape; The water bath drafting device comprises a water bath pool (1), a water guide plate (2), a filter box (4), a drafting assembly, a circulating heating assembly and a cooling assembly; the water guide plate (2) is arranged inside the water bath pool (1) in an inclined manner; the circulating heating assembly is used to drive the water body to circulate and flow and heat the water body; when the water body flows through the water guide plate (2), the cooling assembly is used for cooling; the drafting assembly is used to press the filament bundle into the water on the water guide plate (2) for water bath; the filter box (4) is used to filter impurities in the water body; In step S2, the cooling assembly comprises a blowing cooling assembly and a heat exchange assembly; the blowing cooling assembly is used to blow and cool the filter box (4), and then cool the water body flowing through the filter box (4); the heat exchange assembly comprises a heat exchange box (40) for storing a heat exchange medium; the heat exchange box (40) exchanges heat with the water body to cool the water body by heat exchange; In step S3, two filter boxes (4) are arranged on the water guide plate (2); the filter boxes (4) are covered by fixed covers (35) outside; axial flow fan blades are arranged in mounting boxes (34), the mounting boxes (34) are communicated with the fixed covers (35) through two connecting pipes (37), when the axial flow fan blades rotate, the two filter boxes (4) inside the two fixed covers (35) are blown and cooled through the two connecting pipes (37); then the temperature of the water body gradually decreases after flowing through the two filter boxes (4); In step S3, the two filter boxes (4) are each provided with a water baffle (6) and a filter screen (7); the two water baffles (6) divide the water guide plate (2) into three sections, and then divide the water body above the water guide plate (2) into a high-temperature zone, a medium-temperature zone and a low-temperature zone from top to bottom; the spinning is sequentially subjected to water bath drafting in the high-temperature zone, the medium-temperature zone and the low-temperature zone under the driving of a guide roller (11) and a traction roller (12).

2. The method of producing polylactic acid fiber according to claim 1, characterized by, In step S2, the temperature regulation of the water bath drafting device is as follows: Step S21: setting the highest heating temperature of the heating box (28) according to the high and low of the ambient temperature, and adjusting the highest temperature of the water body; Step S22: setting the running power of the water pump, adjusting the flow rate of the water body, driving the blades (32) in the transmission box (31) to rotate through the flow of the water body, and then driving the axial flow fan blades of the blowing cooling assembly to rotate to blow and cool the filter box (4); Step S23: testing the water temperature of each region on the water guide plate (2), if the expected temperature is reached, step S3 is performed; if the expected temperature cannot be reached, steps S21 and S22 are returned to adjust again.

3. The method of producing polylactic acid fiber according to claim 2, characterized by, In step S2, if the ambient temperature is too high and the expected cooling effect cannot be achieved by the air blowing heat dissipation assembly alone, a heat exchange box (40) is installed in the water bath drafting device, and the water body is cooled by heat exchange with the heat exchange medium in the heat exchange box (40).

4. The method of producing polylactic acid fiber according to any one of claims 1 to 3, characterized by, In step S3, the drafting assembly includes a godet roller (11), a traction roller (12), a first press roller (13), a second press roller (14), and a third press roller (15); the godet roller (11) and the traction roller (12) are respectively arranged at both ends of the water bath pool (1); the godet roller (11) and the traction roller (12) rotate at different speeds to guide and draft the PLA fiber tow.

5. The method of producing polylactic acid fiber according to claim 4, characterized by, The first press roller (13), the second press roller (14), and the third press roller (15) are all arranged above the water deflector (2) to press the PLA fiber tow into the water above the water deflector (2); two fixed plates (16) are rotatably installed on the side wall of the water bath pool (1); the second press roller (14) and the third press roller (15) are both installed on the two fixed plates (16) through bearings and can move with the fixed plates (16).

6. The method of producing polylactic acid fiber according to claim 5, characterized by, In step S3, the method for spinning the PLA fiber into the water bath drafting device is as follows: Step S31: winding the spinning obtained in step S1 on the godet roller (11); Step S32: passing one end of the spinning on the godet roller (11) under the first press roller (13), the third press roller (15), and the second press roller (14) of the drafting assembly, and then winding and connecting with the traction roller (12); Step S33: rotating the fixed plate (16) to drive the second press roller (14) and the third press roller (15) to move downward through the fixed plate (16) until the fixed plate (16) is parallel to the water deflector (2); and then pressing the spinning into the water above the water deflector (2) through the second press roller (14) and the third press roller (15).

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